Field of the Invention
The present invention relates to a method of and apparatus for weather resistance test, and, more particularly to a method of and an apparatus for a weather resistance test of plastics, paint, ink, pigment, fiber with which the results obtained can satisfactorily simulate the outdoor natural deterioration.
Hitherto, when it is intended to test the weather resistance of plastics and paint or the like, a weather meter in accordance with any of JIS (Japanese Industrial Standards) B7751 to 7754 is generally used. Each of the weather meters of the types described above comprise a light sources such as a carbon arc lamp or a xenon arc lamp as to have the beams from this light source applied to the samples As a result, this allows an accelerated weathering test to be carried out.
However, the intensity of the ultraviolet rays radiated from the light source of the above-described type weather meter to be applied to the samples is, in general, limited to an unsatisfactory level of substantially 6 mW per 1 cm.sup.2 of the surface of the sample to be tested. Therefore, it takes several hundred hours or longer to measure or evaluate the characteristics of the ultraviolet ray deterioration which will occur to equate with the deterioration caused by the sun's rays in one year.
Furthermore, a method in which all of the samples in each of the lots are subjected to the test has been so far employed in general. Therefore, it takes an excessively long time to complete the test and to evaluate the results, causing a problem in terms of efficiency.
To this end, in order to overcome the above-described problems, the inventors of the present invention disclosed the following weather meter in Japanese Patent Laid-Open Nos. 60-117128 and 60-117129, that is, a weather meter serving as a pre-weather meter for performing a pre-weather resistance test was disclosed, which allows ultraviolet ray deterioration to be evaluated in a significantly shortened time, for example, in one tenth or less of the time taken in a conventional test period of time and which involves means for applying intense ultraviolet rays of substantially 50 mW or more per 1 cm.sup.2 of the surface of the sample to be tested by using a metal halide lamp beam applied to the samples of each of the lots before having the samples subjected to the weather meter.
It is preferable for the weather resistance test to be conducted under the physical conditions similar to the actual conditions with which the samples such as plastics or paint are subjected. In particular at night, not only the sample is subjected to a state in which no sun rays are applied and of low temperatures but also it can be readily subjected to a dew or moisture condensed state due to the low temperatures at night.
Therefore, it is preferable for the weather resistance test or its pre-test to be made under such dew condensation conditions in order to obtain test results which can simulate the natural outdoor deterioration.
Hitherto, as a method to make such dew condensation conditions for samples, a method was disclosed in Japanese Patent Publication No. 55-13541 in which samples are watered. However, such watering method cannot faithfully simulate actual dew condensation conditions and this is unsatisfactory.
The inventors of the present invention have conceived a method of providing an actual dew condensation state for samples by adjusting the temperature of the sample and both the temperature and the humidity of the ambient air surrounding it. Then the inventors have disclosed the following weather meter in Japanese Patent Laid-Open No. 62-297744. This weather meter is arranged in such a manner that temperature adjusting means is provided for a sample holder and a humidifier is disposed in a chamber of the region in which the thus-provided sample holder is disposed, and by making specific working conditions through control means, the temperature of the sample is lowered below its dew point during an interruption of radiation from the ultraviolet ray source, causing the sample to be brought to a dew condensed state which approximates natural dew condensation.
As means to form dew condensation on the surface of the sample, a method of spraying cooling water to the reverse side of the sample was disclosed, and another method is also disclosed in Japanese Patent Laid-Open No. 58-90146 in which the sample is cooled down by means of a thermoelectric cooling element.
The inventors have found a fact that spot patterns appear on the surface of the sample and the color of the surface of the sample considerably changes in accordance with time lapse as shown in FIGS. 10A and 10B of a microphotograph of the surface of the sample when the above-described dew condensation process is added to the accelerated weathering test in which ultraviolet rays are applied to the sample, where FIG. 10A is a metallurgical microphotograph, enlarged by 200 times, of the surface of the sample which has not been subjected to the test as yet, while FIG. 10B is the same enlarged by 200 times, of the surface of the sample which has been subjected to the weather resistance test for 50 hours. In addition, a fact has been found that the above-described phenomenon particularly appears significantly when this dew condensation process is added to the above-described accelerated weathering test in which the intensity of the ultraviolet rays to be applied is strong.
Such a spot pattern or significant color change do not appear in the case where the sample is placed outdoor naturally. Therefore, this phenomenon presents a serious problem in making the simulation between the natural deterioration and the results of the weather resistance test.
Such spot patterns can be caused from the following reason: impurities contained in the condensed dew appeared on the surface of the sample during the dew condensation process or substances extracted from the sample due to the dew condensation are adhered to the surface of the sample; and then the extraneous matter on the surface of the sample is baked on this surface of the sample due to the lens effect of the residual condensed dew during the application of the ultraviolet rays performed after the dew condensation process; as a result, the above-described spot pattern can be generated.
In order to prevent the spot pattern, it might be considered feasible to employ a method in which the sample is slanted or stood erect for the purpose of having the residual dew on the surface of the sample allowed to fall, another method in which air is blown for the purpose of blowing off the dew, and a still further method in which the residual dew on the surface of the sample is dried up as to be readily removed. However, any of these methods can not achieve a satisfactory effect.